Disable back gesture in Launcher after reboot

It needs to be ensured that `updateDisallowBack` is called at startup after views are created.

Bug: 318786031
Flag: NONE
Test: Manual, i.e. verifying that back gesture is disabled after rebooting the device
Change-Id: I32812101c0e159f5cba41ab419f86de760449906
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index e0e35a4..9ac991f 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -515,6 +515,7 @@
         mStateManager = new StateManager<>(this, NORMAL);
 
         setupViews();
+        updateDisallowBack();
 
         mAppWidgetManager = new WidgetManagerHelper(this);
         mAppWidgetHolder = createAppWidgetHolder();